module Data.Digest.CRC16
( CRC16(..)
) where
import Data.Bits
import Data.ByteString as BS
import Data.Vector.Unboxed as V
import Data.Word
import Data.Digest.CRC
newtype CRC16 = CRC16 { crc16 :: Word16 } deriving (Show, Eq, Ord)
instance CRC CRC16 where
type CRCWord CRC16 = Word16
initCRC = CRC16 0
crcWord = crc16
updateDigest = updateDigest16
crcTable = table
updateDigest16 :: CRC16 -> ByteString -> CRC16
updateDigest16 crc = BS.foldl go crc
where
go (CRC16 crc') b8 =
let idx = fromIntegral (crc' `xor` b16) .&. 0xff
b16 = fromIntegral b8
in CRC16 ((table ! idx) `xor` ((crc' `shiftR` 8) .&. 0x00ffff))
table :: V.Vector Word16
table = V.fromList
[ 0x0000, 0xc0c1, 0xc181, 0x0140
, 0xc301, 0x03c0, 0x0280, 0xc241
, 0xc601, 0x06c0, 0x0780, 0xc741
, 0x0500, 0xc5c1, 0xc481, 0x0440
, 0xcc01, 0x0cc0, 0x0d80, 0xcd41
, 0x0f00, 0xcfc1, 0xce81, 0x0e40
, 0x0a00, 0xcac1, 0xcb81, 0x0b40
, 0xc901, 0x09c0, 0x0880, 0xc841
, 0xd801, 0x18c0, 0x1980, 0xd941
, 0x1b00, 0xdbc1, 0xda81, 0x1a40
, 0x1e00, 0xdec1, 0xdf81, 0x1f40
, 0xdd01, 0x1dc0, 0x1c80, 0xdc41
, 0x1400, 0xd4c1, 0xd581, 0x1540
, 0xd701, 0x17c0, 0x1680, 0xd641
, 0xd201, 0x12c0, 0x1380, 0xd341
, 0x1100, 0xd1c1, 0xd081, 0x1040
, 0xf001, 0x30c0, 0x3180, 0xf141
, 0x3300, 0xf3c1, 0xf281, 0x3240
, 0x3600, 0xf6c1, 0xf781, 0x3740
, 0xf501, 0x35c0, 0x3480, 0xf441
, 0x3c00, 0xfcc1, 0xfd81, 0x3d40
, 0xff01, 0x3fc0, 0x3e80, 0xfe41
, 0xfa01, 0x3ac0, 0x3b80, 0xfb41
, 0x3900, 0xf9c1, 0xf881, 0x3840
, 0x2800, 0xe8c1, 0xe981, 0x2940
, 0xeb01, 0x2bc0, 0x2a80, 0xea41
, 0xee01, 0x2ec0, 0x2f80, 0xef41
, 0x2d00, 0xedc1, 0xec81, 0x2c40
, 0xe401, 0x24c0, 0x2580, 0xe541
, 0x2700, 0xe7c1, 0xe681, 0x2640
, 0x2200, 0xe2c1, 0xe381, 0x2340
, 0xe101, 0x21c0, 0x2080, 0xe041
, 0xa001, 0x60c0, 0x6180, 0xa141
, 0x6300, 0xa3c1, 0xa281, 0x6240
, 0x6600, 0xa6c1, 0xa781, 0x6740
, 0xa501, 0x65c0, 0x6480, 0xa441
, 0x6c00, 0xacc1, 0xad81, 0x6d40
, 0xaf01, 0x6fc0, 0x6e80, 0xae41
, 0xaa01, 0x6ac0, 0x6b80, 0xab41
, 0x6900, 0xa9c1, 0xa881, 0x6840
, 0x7800, 0xb8c1, 0xb981, 0x7940
, 0xbb01, 0x7bc0, 0x7a80, 0xba41
, 0xbe01, 0x7ec0, 0x7f80, 0xbf41
, 0x7d00, 0xbdc1, 0xbc81, 0x7c40
, 0xb401, 0x74c0, 0x7580, 0xb541
, 0x7700, 0xb7c1, 0xb681, 0x7640
, 0x7200, 0xb2c1, 0xb381, 0x7340
, 0xb101, 0x71c0, 0x7080, 0xb041
, 0x5000, 0x90c1, 0x9181, 0x5140
, 0x9301, 0x53c0, 0x5280, 0x9241
, 0x9601, 0x56c0, 0x5780, 0x9741
, 0x5500, 0x95c1, 0x9481, 0x5440
, 0x9c01, 0x5cc0, 0x5d80, 0x9d41
, 0x5f00, 0x9fc1, 0x9e81, 0x5e40
, 0x5a00, 0x9ac1, 0x9b81, 0x5b40
, 0x9901, 0x59c0, 0x5880, 0x9841
, 0x8801, 0x48c0, 0x4980, 0x8941
, 0x4b00, 0x8bc1, 0x8a81, 0x4a40
, 0x4e00, 0x8ec1, 0x8f81, 0x4f40
, 0x8d01, 0x4dc0, 0x4c80, 0x8c41
, 0x4400, 0x84c1, 0x8581, 0x4540
, 0x8701, 0x47c0, 0x4680, 0x8641
, 0x8201, 0x42c0, 0x4380, 0x8341
, 0x4100, 0x81c1, 0x8081, 0x4040
]